1. Field of the Invention
The present invention relates to a broadband terminal equipment for congestion control in the ring structure and its control method. In particular, the invention relates to a broadband terminal equipment provided with MGFC (Multi-access Generic Flow Control) for preventing congestion between a broadband network terminator and a broadband terminal in the multi-access ATM (Asynchronous Transfer Mode) subscriber premises network having a single ring structure and to a multiaccess generic flow control method.
2. Description of the Conventional Art
The B-ISDN (Broadband Integrated Service Digital Network) aims at accommodating not only audio and slow data service provided in the conventional public network but also video and fast data service. For accommodation of slow and fast services, the ITU-T introduced ATM as a transfer method of the B-ISDN.
As shown in FIG. 1 the B-ISDN is divided into a subscriber premises network(101), a broadband access network (102) and an interoffice network (103, 104) according to the equipment which forms a network and its physical position.
The subscriber premises network(101) comprises broadband terminal equipments and a network terminator. In the subscriber premises network (101), there generally exist several broadband terminals such as PC, set-top box and video telephone (204, 214, 224). As the method of connecting them to one user network interface of the public network nodes (201, 211, 221), star structure (203), bus structure (213) and single ring structure (223) are considered, as shown in FIG. 2. The present ATM-related technical standards are, for the most part, focused on the physical point-to-point formation of star structure (203).
GFC(Generic Flow Control) for congestion control of point-to-point formation in the star structure (203) is decided as a standard in the study group 13 of ITU-T, but multi-access ATM technology of shared media base like a ring or bus structure is wholly lacking.
In the star-structured ATM subscriber premises network (203), a broadband terminator (202) which functions like an ATM switch or a multiplexer must be used and so it is suited for the structure of large-scale business subscriber premises network. In the Case of small-scale business subscribers and residential subscribers it is economical to build the subscriber premises network with only an ATM card which performs a multi-access function without investing in the ATM switch or multiplexer in the early stage. The traffic of these subscribers will consist mainly of a downward traffic to subscriber premises network from public network. As it does not require high reliability like public network, the multi-access ATM subscriber premises network (223) having a single :ring structure is efficient to build a subscriber premises network economically.